There are many known machines and methods known for making bags and pouches. Intermittent motions machines are often used to make some pouches, such as those used in the medical field. Typically such medical pouches are made from a laminate film or a mono film. Laminate film, as used herein, includes a film made up of two or more layers, such as an upper layer that is sealed in various locations to a lower layer. The layers can be comprised of different materials.
Generally, the prior art provides for intermittently advancing the laminate film. When the film is stationary, a sealing platen, cross sealer, or longitudinal sealer is lowered into contact with the film. Through a combination of pressure, temperature and time, an upper layer of the laminate is sealed to a lower layer. The platen typically includes a sealing pattern for making more than one pouch. The platen is raised after the seal is formed, and the film is advanced. A downstream cutting section cuts the film into individual pouches.
Platen, as used herein, includes sealing surfaces that form seals in both the machine and cross directions, form multiple seals in the cross direction at different machine direction locations, or form multiple seals in the machine direction at different cross direction locations. Cross sealer, as used herein, is a sealer that makes a seal that extends a greater distance in the cross direction than the machine direction. Longitudinal sealer, as used herein, is a sealer that makes a seal that extends a greater distance in the machine direction than the cross direction. Platens, cross and longitudinal sealers can have multiple sealing surfaces. Multiple sealing surfaces, as used herein, includes sealing die surfaces that form more than one seal, either in the same or different directions.
Many prior art machines have a motor located beneath the machine, and linkages translated the force to the platen. Linkage, as used herein, includes mechanical connection between two items that provides for the transmittal of force or movement from the first item to the second item, and can include pivot points, etc. The linkages are complex, and sometimes included an eccentric cam that either rocked back and forth, or fully rotated, to cause the platen to move up and down. The linkages in such systems are subject to wear and maintenance, as well as causing looseness in the system which could result in improper sealing. Also, such systems require a load cell to measure the force applied by the platen, and required loss motion to control the force.
Given the nature of the medical industry and the type of items being packaged, medical pouches are often made with strict tolerances. Prior art U.S. Pat. No. 6,452,354 (hereby incorporated by reference) attempted to teach how to make pouches adequate for the medical field. Generally, it taught to use a single servo motor to drive the sealing platen, and to use a force transducer to measure the force exerted by the platen. The force was used as feedback to control the servo motor. U.S. Pat. No. 6,452,354 used the force feedback to purportedly account for process variations such as properties of the material used, wear of a rubber backing surface, etc.
However, because this prior art patent uses force as its main control parameter, it requires an add-on force transducer and cannot rely on already available servo motor feedback, which adds cost and complexity. Also, it teaches the use of a single servo motor, which can result in an unbalanced platen (i.e., more force on one side than the other). Moreover, it is primarily concerned with applying sufficient force and does not recognize that the force should be controlled to prevent fracturing of the laminate film. Rather, it teaches to control excess force merely with a safety relay to prevent damage to the machine.
Another prior art machine, described in U.S. patent application Ser. No. 12/265,428 and PCT application PCT/US09/60620, and sold as the PDI® 600SS pouch machine (shaped seal), and made by CMD® Corp. provided for a platen driven by two vertically mounted Exlar® roller screw actuators (also called linear actuators). Linear actuator, as used herein, is a device that converts some kind of power, such as hydraulic or electric power, into linear motion.
The actuators drive the platen up and down, using guides mounted beneath the actuator, toward the midline in the cross direction, away from the edge of the machine. A clevis mount is used. Two actuators are used because of the force needed to drive the platen down, into a rubber backing, to make the seal. This design avoids the linkages of the prior art using under mounted servo motors, However, it requires two actuators (which can be expensive) to obtain the desired force, and requires space above the machine for the actuator (which moves vertically) to be mounted, and cannot be mounted beneath the machine.
Prior art pouch machine sealers typically included a sealing die that has the sealing surface thereon. The sealing die is often attached to a die backing member. The sealing die can be affixed to the die backing member, such as with cap screws. However, it is sometimes desirable to change the sealing die, due to wear or to provide a different sealing profile. In such cases the entire sealer could be changed, but that can be costly and time consuming. Unscrewing the sealing die from the die backing member requires a tool and is time consuming. Some prior art machines have quick change sealing dies, that include a spring loaded L clip. Such clips are expensive.
Accordingly, a pouch machine that moves a platen, cross sealer, or longitudinal sealer that avoids complex linkages, applies force evenly, and is not excessively expensive is desirable. Also, a sealing die that can be easily removed and replaced, without expensive clips, is also desirable.